my question is about what a private key is? and where would I find it on an ewallet like metamask?
You can export your private key in metamask doing the following
if you only want to export a single account to another wallet, you can click the "Export Private Key" option on the Account Detail view. Currently, that's the key icon:
Source : Exporting a MetaMask Account
Already answered question about the private key : What is the Private Key?